We are doing the same with DGD age almost 2.5 and it's been fine. She was useless last week playing out in the garden, probably just too busy doing her work! This week there have been no accidents. We make sure she uses the potty before we go anywhere (she was even fine going to my mums which is well over an hour away), before going for a nap etc.
She loves her wee pants (smallest size available!) and gets to choose which pair she wears every day. Just the one pair a day now. 
The parents were putting her nappy pants on when they went out so had to be told to cease and desist or she'd only end up confused, not toilet trained.
I have a waterproof sheet on her bed figuring it's easier to remove and wash than the mattress cover. She still has her nappy at night but not for her afternoon nap ... no accidents yet, clever wee girl!
Loads of pants etc and potties downstairs and upstairs in her room.
DD uses stickers at home, our Minnie Mouse potty has a handle she pulls to get a big cheer! 